The invention concerns the construction of loudspeakers, particularly the construction of driving systems for such loudspeakers, and the reciprocal assignment of such loudspeakers.
In the state of the art it is known to build driving systems for loudspeakers in such a way, that a permanent magnet is connected to so-called yoke or back-closing parts, where a ring gap is left in the yoke parts into which the voice coil, which is connected to the loudspeaker, can later dip. Such an arrangement containing a permanent magnet which is magnetized axially to the longitudinal axis of the magnet system is indicated in DE-A-4113017 for example. Magnet systems with two permanent magnets are indicated in the publications DE-A-4234069 and DE-A-4225156.
In addition to this, magnet systems are known which contain permanent magnets that are magnetized radially to the longitudinal axis of the magnet system. These permanent magnets are either made in one piece or comprise a series of linked permanent magnet segments. Such arrangements are known from WO 93/03586 for example. These arrangements also contain back-closing parts which conduct the magnetic flux provided by the permanent magnets, so that sufficient induction is available for the ring gap.
The expensive manufacture as well as the heavy weight and the large volume of such systems or loudspeakers are considered to be disadvantages. It is therefore the task of the invention to create a magnet system which avoids the disadvantages of the state of the art.
This task is fulfilled by the features of a loudspeaker with a magnet system comprising at least one permanent magnet, which is magnetized crosswise to the longitudinal axis of the magnet system and has receiving parts that support the permanent magnet, or are connected thereto, characterized in that the receiving parts are made exclusively of a material that has paramagnetic or diamagnetic properties.
The basic idea of the present invention is to utilize the stray flux produced by a radially magnetized permanent magnet to drive a voice coil. This makes it possible to build the receiving parts for the permanent magnet from a paramagnetic or diamagnetic material. The result is that a considerable space and weight reduction is obtained, since the geometric specifications for the back-closing parts, which according to the state of the art must be taken into consideration for conducting the magnetic flux inside of these parts, are insignificant according to the invention. The invention strongly simplifies the manufacture of magnet systems as well, because the operating steps which are necessary to link the otherwise customary back-closing parts according to the state of the art, are omitted. The receiving part of the invention only forms the rearward closure of the loudspeaker, or a support structure for the permanent magnet and the remaining loudspeaker components.
Since a cone loudspeaker usually has a basket which is connected to the magnet system, it is possible to manufacture one-piece units of the receiving part and loudspeaker basket in a very cost-effective manner because the receiving part of the invention has no function with regard to the magnetic flux, nor should it have any in view of the stray flux utilization.
Plastics, metal and metal alloys are suitable materials for manufacturing receiving parts or units comprising a receiving part and a loudspeaker basket. Using metal to manufacture receiving parts in the preceding sense has special advantages since these materials also provide good heat transfer in the driving system area.
A particularly effective use of the stray flux generated by the permanent magnet is provided when the magnet system is built with a loudspeaker having another voice coil which is located at a radial distance from the other jacket surface of the permanent magnet. In that case the stray flux generated by the permanent magnet is used by both coils to drive a diaphragm.
Two or more permanent magnets can be arranged with a reciprocal axial space in the direction of the longitudinal axis of the magnet system to increase the stray flux required to drive the diaphragm. In such a configuration each of these permanent magnets can be surrounded by a voice coil on its inner and/or outer jacket side. If additional voice coils are used to drive a diaphragm for example, it is necessary to link these voice coils rigidly with each other. The magnet system of the invention can also be modified so that for example all the coils arranged on an inner jacket surface of the permanent magnet can be used to drive one diaphragm, and all the coils arranged on the other jacket surface can be used to drive another diaphragm.
A loudspeaker can also be constructed so that each voice coil is arranged on a voice coil support, wherein the voice coil support is a common voice coil support for the two voice coils, wherein each voice coil support has a first end and a second end, and that the first end at least is connected to a diaphragm.
If the respective voice coil support is tube-shaped, and if the first end of this voice coil support is connected to a first diaphragm, and the second end of this voice coil support is connected to a second diaphragm, and if both diaphragms and their supports etc. are constructed identically, such an arrangement can be used as a dipole radiator, for example to produce a diffuse sound field for a Dolby sound reproduction. According to the state of the art such diffuse sound fields are produced when two identical but inversely poled loudspeakers with separate volumes are used. But the desired effects can only be achieved with such arrangements when both loudspeakers have reproduction characteristics that are identical to within 1 to 2 dB. If these conditions are not upheld, the respective sound event can be perceived as coming from the front or from the back. It can easily be seen that the identity of the reproduction characteristics can only be assured at a considerable production cost. However if the arrangement for producing a diffuse sound field is built in the manner described above, deviations which are provoked for example by production-caused diaphragm differences or unavoidable manufacturing differences during the loudspeaker assembly can be balanced or minimized by having the production-caused differences of all diaphragms etc. become effective in every operating condition through a mechanical coupling of both diaphragms.